Acoustic horn arrangement

Abstract

An acoustic horn arrangement including an acoustic horn, a first sound driver operable to drive the acoustic horn and a second sound driver further operable to drive the acoustic horn. The acoustic horn arrangement also including an interface region where sound from the second sound driver transfers into the acoustic horn to combine with sound from the first sound driver, wherein the interface region is adapted to reduce changes in a beam angle measure of the acoustic horn as a function of frequency.

The invention claimed is: 
     
       1. An acoustic horn arrangement including:
 an acoustic horn, the acoustic horn including a throat entrance and a mouth exit and further including an outwardly flaring wall region extending from the throat entrance to the mouth exit; 
 a first sound driver operable to drive the acoustic horn, the first sound driver located at the throat entrance of the acoustic horn; 
 a second sound driver further operable to drive the acoustic horn; and 
 an interface region located in the wall region of the acoustic horn where sound from the second sound driver transfers into the acoustic horn to combine with sound from the first sound driver, wherein the interface region includes at least one aperture that is elongate generally in a direction of sound propagating down the acoustic horn and wherein the at least one elongate aperture is located to substantially minimise a proportion of area of the at least one elongate aperture that lies on a centre line of the acoustic horn to reduce changes in a beam angle measure of the acoustic horn as a function of frequency. 
 
     
     
       2. An acoustic horn arrangement as claimed in  claim 1 , wherein the sound from the first sound driver is generated in a first frequency range and the sound from the second sound driver is generated in a second frequency range. 
     
     
       3. An acoustic horn arrangement as claimed in  claim 1 , wherein the acoustic horn arrangement has constant directivity characteristics. 
     
     
       4. An acoustic horn arrangement as claimed in  claim 1 , wherein the configuration of the acoustic horn arrangement defines vertical and horizontal directions with respect to the acoustic horn and wherein the interface region is adapted to reduce changes in the vertical beam angle of the acoustic horn as a function of frequency. 
     
     
       5. An acoustic horn arrangement as claimed in  claim 1 , wherein the at least one elongate aperture is oriented to follow a streamline of the sound from the first sound driver. 
     
     
       6. An acoustic horn arrangement as claimed in  claim 1 , wherein the at least one elongate aperture has a rectangular slit configuration. 
     
     
       7. An acoustic horn arrangement as claimed in  claim 1 , wherein the at least one elongate aperture has a tapered or wedge shape slit configuration. 
     
     
       8. An acoustic horn arrangement as claimed in  claim 7 , wherein a width of the tapered or wedge shape slit configuration is held to be a substantially constant fraction of a dimensional characteristic of the acoustic horn. 
     
     
       9. An acoustic horn arrangement as claimed in  claim 8 , wherein the dimensional characteristic is the circumference of the acoustic horn. 
     
     
       10. An acoustic horn arrangement as claimed in  claim 8 , wherein the dimensional characteristic is the cross sectional area of the acoustic horn. 
     
     
       11. An acoustic horn arrangement as claimed in  claim 1 , wherein the at least one elongate aperture has a kite shaped configuration. 
     
     
       12. An acoustic horn arrangement as claimed in  claim 1 , wherein the at least one elongate aperture has a truncated kite shape configuration. 
     
     
       13. An acoustic horn arrangement as claimed in  claim 1 , wherein the acoustic horn has a rectangular cross-section. 
     
     
       14. An acoustic horn arrangement as claimed in  claim 1 , wherein the acoustic horn has an elliptical cross-section. 
     
     
       15. An acoustic horn arrangement as claimed in  claim 1 , wherein the interface region is further adapted to modify a cavity resonance frequency caused by a cavity formed between the interface region and the second sound driver to substantially minimise the effect of the cavity resonant frequency on the on-axis frequency response of the first sound driver. 
     
     
       16. An acoustic horn arrangement as claimed in  claim 15 , wherein the interface region is adapted to modify the cavity resonance frequency by a phase plug member incorporating apertures connecting the air space of the second sound driver to the air in the acoustic horn. 
     
     
       17. An acoustic horn arrangement including an acoustic horn operable to be driven by a first sound driver, the acoustic horn arrangement further including two or more additional sound drivers each introducing sound into the acoustic horn by a respective interface region, located in the wall region of the acoustic horn, wherein the respective interface region for each of the two or more additional sound drivers is adapted to reduce changes in the beam angle of the acoustic horn as a function of frequency in accordance with  claim 1 . 
     
     
       18. A sound reproduction system including the acoustic horn arrangement of  claim 1 . 
     
     
       19. An interface arrangement for transferring sound from a secondary sound driver having a loudspeaker cone into an acoustic horn driven by a first sound driver located at a throat entrance of the acoustic horn, the interface arrangement including a phase plug member to define the path length and volume of air of a cavity formed between a surface of the loudspeaker cone of the secondary sound driver and an interface region, located in an outwardly flaring wall region of the acoustic horn, wherein the phase plug member incorporates apertures that extend close to the surface of the loudspeaker cone to connect the air space immediately under the loudspeaker cone with the air in the acoustic horn to form an acoustic resonator and modify the cavity resonant frequency to substantially minimise the effect of the cavity on the on-axis frequency response of the first sound driver.